Industry statistics reveal that a fair percentage of control loops are controlled manually, and are not automated.   This fact was brought home last week, when a caller told us he needed “something to adjust the valve position so that the valve stays where it’s been set.  And it’s real important that it can’t accidentally go off its own”.   

What he was describing is what we call a manual station.   It’s a controller where the 4-20mA current output stays fixed where it is until someone pushes buttons on on the front of the controller: up to manually raise the output value, and down to manually lower it.  Typically, the output value is displayed for the operator as a digital number from 0 to 100 percent.  

So what’s available to fill the bill?
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